When working on agricultural fields, satellite-supported positioning systems, among other things, are used to place individual seeds or plants at specific positions in the soil during seeding or planting operations. In this way one can achieve certain patterns (DE 102 51 114 A1) that also enable equipment lanes for field work, in particular weeding, in a direction across or diagonal to the original planting direction (DE 10 2005 101 686 A1) or that optimize solar irradiation (DE 10 2007 040 511 A1).
Usually the pattern is planned in advance on a computer, where the coordinates at which the seeds or plants are placed in the soil are established in order to achieve the desired pattern, or a first row is planted in the field and the subsequent rows are directed laterally to the first row opposite the forward direction of the seeding or planting machine (O. Schmittmann et al., “Development of a Precision Planter Drive for Coordinate-Controlled Planting of Seeds,” Landtechnik 2010, 286).
This procedure works relatively well as long as the field is completely horizontal, since in the prior art the position determining means used to control the seeding or planting machine is based only on two-dimensional (horizontal) coordinates, i.e., it is based on a projection of the field at a (vertical) elevation of 0. In this regard see FIG. 1, which shows a projection of a square field in the horizontal plane with typical points for seeding or planting planned in two-dimensional space (or points that gradually result during the work on the field). However, when the field is inclined in one or two horizontal directions, for example has a mound or a depression as shown in FIG. 2, a planting of seeds or plants based only on a two-dimensional point determination leads to errors, since in going up a slope or going back down the slope, the seeding or planting machine in fact takes a different return path than the only horizontal distance measurement shows (because of the slope). For a slope angle α, the path l that is actually traversed on the return is the horizontally measured distance x multiplied by a factor of 1/cos α (see FIG. 3). Because of this, the seed spacing in the forward direction in such cases is too large by the said factor, which leaves a desired working of the field in the transverse or diagonal direction impossible or at least makes it difficult, since the planned row spacings are no longer maintained.
This problem is easily recognized on the sides of the central hill on the field in FIG. 2: If the seed or plant material is planted with a single-row machine on the basis of a two-dimensional map and position determination, the distances between adjacent plants on the inclined surfaces will be greater than in the plane, both in the x and y directions. Working between the rows with a multi-row implement will not be possible because of the varying distances between the plants. It should be noted that probably a multi-row seeding or planting machine will actually be used, and with such a machine, the spacings between adjacent plants across the forward direction will necessarily remain constant, but they will vary along the forward direction going up and down slopes.
It was in fact proposed, for work on a hillside, to take into account the then reduced spacings projected on the horizontal, and thus to put adjacent swaths in the horizontal projection closer to each other than on a horizontal field (EP 1 475 609 A2), but this does not have any effect on the planting of seeds or plants in the forward direction of the machine. The said error would thus continue to exist. This is analogously true even for advance path plannings that take into account the three-dimensional shape of the field (J. Jin et al., Coverage Path Planning on Three-Dimensional Terrain for Arable Farming, Journal of Field Robotics 28(3), 424-440 (2011) and I. A. Hamed, Intelligent Coverage Path Planning for Agricultural Robots and Autonomous Machines on Three-Dimensional Terrain, J. Intell. Robot Syst. (2014) 74:965-983).